pfn_to_bfn
unsigned long bfn1 = pfn_to_bfn(page_to_pfn(vec1->bv_page));
unsigned long bfn2 = pfn_to_bfn(page_to_pfn(page));
unsigned long bfn = pfn_to_bfn(XEN_PFN_DOWN(paddr));
phys_addr_t bus_addr = pfn_to_bfn(XEN_PFN_DOWN(p)) << XEN_PAGE_SHIFT;
next_bfn = pfn_to_bfn(xen_pfn);
if (pfn_to_bfn(++xen_pfn) != ++next_bfn)